Photographic multicolor images



April 24, 1945.

PHOTOGRAPHI C MULT I COLOR IMAGES Filed Feb. 17, 1942 I l I 7-50 700 650 600 500 500 450 400mp' l l l l I 750 7010 6:150 600 5.50 500 450 400m 1 750 700 650 600 550 500 450 Mflmp 50 700 650 600 am m0 4150 4mm,

w. SCHNEIDER 2,374,505

Patented Apr. 24, 1945 Wilhelm Schneider, Dessau,

Aniline & Film York, N. Y., a corporation of to General Germany, assignor Corporation, New Delaware Application February 17, 1942, Serial No. 431,261

In Germany July 4 Claims.

My present invention relates to photographic multi-color images, and more particularly to an improved process for producing such color photographic images.

In the production of photographic multi-color images according to a subtractive process such as the Technicolor" process or a silver dyestufi bleaching out process copying has generally hitherto been carried out by means of component sensations in 'black-and-white. It has already been proposed directly to copy color negatives onto a photographic multi-layer material. However, this method has hardly been put in practice because one encounters a plurality of difiiculties in such methods. By using a three-layer material for the negative and copying this negative onto a similar material as hitherto proposed there have been obtained only very unfavorable and unsatisfactory results. In such processes for the production of -multi-color images a multi-layer material the single layers of which are sensitized to different spectral ranges has been employed for exposure, the sensitization of the single layers being so chosen that the sum of the sensitizing ranges thereof corresponds with the whole region of the visible spectrum, and each layer being sensitive only to one color. In order to obtain a good color separation one has selected sensitizers the sensitizing curves of which show a descent as steep as possible towards the long-wave region. An improvement of the color reproduction especially of certain spectrally very pure tones in the blue-green to the violet and in the yellow-red can be reached by overlapping the sensitizing ranges of the single layers see, f. i., the French Patent 837,153). The color reproduction of the copy can further be improved by sensitizing the copying material only in three sharp bands in the blue, green and red regions in contrast with the sensitization of the negative material the spectrum of which is to represent an image as exact as possible of the solar spectrum having all mixed colors. To ensure a sharp separation in copying, it has moreover been suggested to use a copying light having a narrowly limited wave range. Finally, it has been proposed to copy component sensations onto multi-layer material into the invisible region of the spectrum in order ranges are separated from one another as far as possible. However, in these copying processes comprising the use of partially invisible rays there are necessary special expedients and steps. Therefore, such processes obviously are disadvantageous when compared with copying processes including the use of white light.

It is an object of my inventionto overcome the drawbacks mentioned above. Another object is to provide a method for directly copying color images onto a photographic multi-layer material in a simple manner. Further objects of the present invention will appear from the following description.

The invention is further illustrated by reference to the accompanying drawing, in which:

Figure 1 shows sensitizing curves of sensitizers of a multi-layer material for exposure according to the invention,

Figure 2 shows absorption curves of the image dyestuffs of a negative material for exposure according'to the invention.

Figure 3 shows sensitizing curves of sensitizers for the copying material in accordance with the invention,

Figure 4 shows absorption curves of image dyestuifs of a copying material in accordance with the invention, and

Figure 5 shows absorption curves of image dyestufls of materials for exposure and reproduction as hitherto used.

The objects of the invention are accomplished by using for exposure a multi-layer material the sensitizing ranges of which overlap and in the layers of which dyestufi images having absorption maxima separate from one another as far as possible are produced, and copying the negatives thus obtained onto a multi-layer material the layers of which have narrow sensitizing ranges, the maxima of each sensitization corresponding to the absorption maxima of the dyestuffs of the image to 'be copied whereas the image dyestuffs of the copying material comply with the requirements of the subtractive image reproduction inasmuch as the absorption maxima of these dyestufi's have normal positions.

For the exposure there is used a photographic multi-layer material which comprises a blueabout 430 to about 460 mp, a green-sensitive layer having a sensitizing range from about 440 to about 630 mu with a maximum at about 540 to about 560 m and a red-sensitive layer having a sensitizing range from about 500 to about 750 m l with a maximum at about 630 to about 650 mu (see Figure 1). It is, however of advantage if the red-sensitive layer additionally exhibits a slight sensitivity in the short-wave blue and the blue-sensitive layer a sensitivity in the longwave red as shown in Figure 1. This additional sensitization serves to reproduce all color tones found in nature as'exact as possible. It has been suggested to give a layer of a multiadditional sensitization which copied and is fundamentally different from the.

additional sensitization which is disclosed in the present application and the maximum of which does not correspond with that of the sensitization of another layer but lies in the outermost regions of the visible spectrum.

According to the present invention the image dyestufl's for the negative material are so selected in departing from the known methods in which the same dyestuffs are employed for exposure andreproduction (see Figure that the distances apart of their absorption maxima are as large as possible. This means, for example, that instead of absorption maxima for the yellow dyestufl of about 450 m for the purple dyestufl of about 540 my and for the blue-green dyestufi of about 620 me there are used dyestuffs having maxima at about 435 m (420-450 m for the yellow dyestuff, at about 545 m (530-560 mp.) for the purple dyestuff and at about 695 m (680-710 m for the blue-green dyestuff as shown in Figure 2. By the displacement of the absorption maxima the overlapping regions of the dyestuffs are reduced and the sensitizing maxima of the positive which lie in the absorption maximum of the negative dyestufl's are likewise farther separated from one another so that an optimum color separation is attained in copying with white light. The maximum sensitizations for the copying material are, for instance, shown in Figure 3. Although the example for the sensitization of the negative holds true in all cases, the maxima of the dyestuffs for the component images of the negative and the proper maximum sensitizations of the positive material may also have another position provided that these maxima are separated from one another as far as possible. It is quite immaterial whether the negative dyestuffs have yellow, purple, and blue-green color tones as hitherto required for the subtractive process. The dyestuffs for the positive on the other hand shall show again the normal colors ofthe subtractive process, for instance, with absorption maxima at about 420-440 m about 520-540 mi, about 640-660 mu as represented in Figure 4. In this way an unobjectionable reproduction in natural colors is obtained without the necessity of using filters absorbing light or special copying lights.

As materials for exposure and copying there may be used layers without dyestuif formers in which the color images are produced successively. However, it is especially advantageous to use layers containing dyestufl formers fast to diffusion. If necessary, the exposure material may be provided with a filter absorbing ultra-violet rays in a similar manner as .described in the French Patent, 837,153. This ultra-violet filter is advanta'geously arranged on the photographic material in the form of a filter layer.

7 The present invention is illustrated by the following example which is not intended to be limiting.

Example A negative material according to the invention on on. IIIH-Cd-Cnflu as the dyestuff former for bluish red the compound of the following formula:

as the dyestuff former for yellow the compound of the following formula:

These dyestuff formers produce dyestufi' images the maximum absorptions of which are widely separated from one another.

The dyestuff formers referred to above and hereafter may be prepared according to U. 8. P. 2,186,849.

As sensitizers for the negative material the sensitizing ranges of which are overlapped the following dyestufis are suitable:

The following sensitizer for green has a maximum of about 550 m l.

. This sensitizer may be prepared by reacting 4.5-

diphenyl-2-methyl-N-thiazolium bromide with the condensation product from N-ethyl benzthiazole-Z-methine-omega-aldehyde, N-ethyl rhodanine and dimethyl sulfate.

The following sensitizer for red has a maximum at about 640 m The following dyestufl serves for the additional sensitization in the red:

N )hHs Its maximum is at about 690 mg.

The intermediate from which this dyestuff is derived can be made according to Example No, page 22, of British Patent 489,335, while substituting lepidine for the l-methyi benzthiazole of the example. The dyestuff can be made according to lines 81 to 91, page 26 of said British patent while utilizing said intermediate in lieu of that employed in lines 81 to 91, page 26 of said British patent.

For the image dyestufls of the positive material 7 ing the negative image the following compound is used as the dyestuffformer for blue:

as the dyestuil former for red:

As the dyestuif former for yellow a compound or the following formula is employed: 1

The positive material is sensitized by using the following dyestuff as the sensitizer for green.

which has its maximum at about 550 m and the following dyestufi as the sensitizer for red:

COOH O=(|J :-cn=c I! N Ca H5 \CIOA I C2H5 which has its maximum I claim:

1. In a process for producing photographic multi-color images, the improvement which comprises exposing to a colored object a photographic multi-layer material each emulsion layer of which contains a sensitizer, the sensitizing range of which overlaps with the sensitizing range of each sensitizer in the other emulsion layers, and each emulsion layer of which contains a dyestuff former capable of producing a dyestuff image with the oxidation products of an aromatic amino developer, said image dyestuffs having absorption maxima which are farther separate from one another than the sensitizing maxima of the corresponding layers, developing the material with said developer to form said dyestufi images and copyobtained onto a photographic multi-layer material the several emulsion layers of which contain sensitizers having narrow sensitizing ranges and sensitizing maxima corresponding to said absorption maxima of the image dyestuflf of the exposure material and dyestuff formers capable of producing dyestuffs with the oxidation products of an aromatic amino developer, said last-named image dyestuffs having absorption maxima which have normal positions.

2. In a process for producing a photographic multi-color image, the improvement which comat about 690 m prises exposing to a colored object a photographic multilayer material having in superposition an outermost silver halide layer sensitized for a.

range up to mediate silver halide emulsion layer sensitized for a range of from about 440 to about 630 Ill 1., said imum within the range of 680 mi to 710 m and said intermediate emulsion layer containing a dyestufl? former capable of producing a magenta dyestufl image with the oxidation products of an developer, the dyestufl. of said image having an absorption maximum'in the range of 530 to 560 m developing said photographic multilayer material with an aromatic copying the negative images so obtained onto a photographic multilayer position an outer silver halide emulsion layer sensitized for a range of from 400 to 500 m with a m and an intermediate silver halide emulsion layer sensitized for a range of 500 to 5'70 mg, with a maximum at about 545 m the sensitizing maxima of the sensitizers of said copying material corresponding to the absorption maxima of the image dyestufis of the exposure material, the layers of said copying material containing dyestufi developer, the dyestufls of said last named images having absorption maxima which have normal positions.

3. The process as defined in claim 2 wherein the innermost layer of the exposure material is sensitized with a rhodacyanine dye in which the methenyl chain interrupted by an N-alkyl rhodanine nucleus serves to link an N -alkyl benzthiazole nucleus to a phenyl substituted N-alkyl thiazoline nucleus and wherein the intermediate trimethenyl chain serves to link an N-alkyl thiazoline nucleus to an N -alky1 benzthlazole nucleus and wherein the innermost layer of the copying material is sensitized with a rhodacyanine dye in which the methenyl chain interrupted by an N- alkyl rhodanine nucleus serves to link an N-alkyl quaternary nucleus to an N-alkyl benzoxazole nucleus and wherein the intermediate layer of said copying material is sensitized with a symmetrical trimethine dye in which the trimethenyl chain serves to link two N-alkyl benzoxazole nuclei and the methenyl chain is substituted in the meso-carbon atom by alkyl.

4. The process as defined in claim 2 wherein the dyestufi former in the outermost layer of the exposure material is a benzoyla'cetanilide in which the benzoyl radical is substituted by an amide group containing a long alkyl chain, wherein the dyestufi former in the intermediate layer of the exposure material is a l-phenyl-5-pyrazolone in material having in superwhich the carbon atom in 3-position is substituted by a stearyl amide phenyl radical, and wherein the dyestufl former in the innermost layer is a naphalkyl chain, wherein the dyestufl former in the intermediate layer of the copyin material is a i-phenyl-li-pyraaolone in which the carbon atom in B-position is substituted by a long alkyl chain and wherein the dyestufl former in the innermost layer of the copying material is a naphthol containing an amino group which is substituted by a lona alkyl chain.

WEI-ELM BCHNEDER. 

